MEASURING COASTAL CHANGE FROM 4D STRUCTURE-FROM-MOTION PHOTOGRAMMETRY (Invited Presentation)

Coastal landforms are dynamic and change regularly as a result of oceanic, meteorologic, hydrologic, and geologic factors. Measurements of topographic change across the diversity of coastal landscapes – including beaches, sea cliffs, dunes, estuaries, inlets, and the human infrastructure present throughout coastal regions – will assist with assessments of historical trends and predictions of future change under scenarios of climate and sea-level change. Here we report on recent advancements of 4D structure-from-motion (SfM) photogrammetry that allow for high resolution and high accuracy measurements of landscape surfaces from single-pass aerial photography. A primary technique incorporates photographs from different acquisition dates into the alignment and camera calibration stages of SfM, which has been shown to result in order-of-magnitude improvements in the accuracy of topographic change measurements when compared to traditional SfM techniques. These photogrammetric advancements have provided the impetus for a series of new single-pass oblique aerial photography flights from small airplane along the U.S. Pacific coast by the U.S. Geological Survey (USGS). We use both USGS and California Coastal Records Project (CCRP) oblique aerial photographs to characterize landscape changes to beaches and sea cliffs, including the ground motions in Big Sur, California before and after the large landslide at Mud Creek on May 20, 2017. These results suggest that widespread and accurate monitoring of coastal change can be conducted with relatively inexpensive endeavors to collect aerial photographs.